In orthopedic procedures, it is often necessary to secure an orthopedic implant to bone and/or to another orthopedic implant. In such cases, an orthopedic fastening system may be provided in which an orthopedic locking screw is used to secure an orthopedic implant to a bone and/or an orthopedic implant to another orthopedic implant.
One exemplary arrangement that utilizes such an orthopedic fastening system is in the case of an intramedullary bone nail. The intramedullary bone nail is used to secure two or more bone pieces together, and orthopedic locking screws are used to secure the bone pieces to the intramedullary bone nail. One exemplary arrangement of an intramedullary bone nail secured to the bone pieces with locking screws is shown in WO 2013/075730 A1.
Another bone screw disclosed in U.S. Pat. No. 8,162,998 includes a radially expandable sleeve with internal threads that is threaded onto a threaded end of the screw.
However, often there is a small radial gap or interval between the outer diameter of the locking screw and the inner diameter of the bore of the orthopedic implant that operably receives the locking screw. For example, the locking screw may have an average outside diameter of 5.0−0.05 mm and the bore may have an average internal diameter of 5.1+0.2 mm. This gap or interval can give rise to up to 0.1+0.25 mm radial play between the locking screw and the orthopedic implant. This radial play can allow shifting and movement of the bone and/or locking screw relative to the orthopedic implant and/or relative to other bone portions secured by the orthopedic implant. Such shifting and movement may slow down or otherwise have a negative effect on healing of the fracture.
In order to eliminate or minimize this play between the connected parts, it is common to use additional screws. This, however, increases the number of parts used and inserted into the body and may increase the necessary healing time.